In elevator systems the giving of calls conventionally occurs with up/down pushbuttons in the elevator lobby, by means of which pushbuttons a passenger expresses his/her desired direction of travel and further, after the elevator has reached the floor on which the passenger is located, his/her desired destination floor by means of pushbuttons in the elevator car. To an increasing extent also so-called destination call systems are used, in which each passenger gives his/her personal destination call already at the departure floor before going into the elevator car. Often a problem in hospitals, senior citizens' housing and many other buildings is that loads of large size, such as hospital beds or wheelchairs, are moved with the elevators, and these take up a lot of the floor area of the elevator car in relation to their weight. In this case situations arise in which new passengers no longer fit into an elevator car, although on the basis of the measured car load there should be adequate free space in the elevator car. As a consequence, an elevator car serving a call stops unnecessarily at an elevator lobby even though the giver of the call does not fit into the elevator car, in which case the transport capacity of the elevator system decreases and passengers become frustrated because they must give their calls again and must wait for the next elevator.
Efforts have been made to solve this problem by adding to the call-giving appliances special pushbuttons that indicate the type of call, by means of which e.g. a passenger moving in a wheelchair can order an elevator car containing sufficient space for a wheelchair. Adding the aforementioned type pushbuttons to the call-giving appliances, however, easily makes the call-giving appliances complicated and confusing to use. In addition, it should be precisely known right from the installation phase of the elevator system which type pushbuttons will be needed during the operating history of the elevator system, because retrofitting new type pushbuttons to the call-giving appliances is an awkward and expensive, even sometimes impossible, procedure. Also the threshold limits of car load weighing devices, which are used to identify the degree of filling of elevator cars, must often be tuned to be unnecessarily small to avoid unnecessary stops.